1. Field of the Invention
The present invention relates to engine oils. More particularly, the present invention relates to overbased detergents for use in engine oils, especially metal-containing neutral and overbased salicylates based on styrenated salicylic acid that provide excellent detergency and clarity in a lubricating oil, and to a method for making such detergents.
2. Description of Related Art
Among the materials that impart detergency to lubricating oils to keep internal engine parts clean and reduce sludge formation in the oil are overbased detergents, particularly calcium sulfonates. These sulfonates are known to be useful as additives for lubricating oils, particularly as a crankcase engine oil for internal combustion engines.
It is known that by use of such overbased detergents equivalent detergency characteristics can be obtained with a lower concentration of additive in a lubricating oil—the higher the alkaline reserve of an additive, the larger the quantity of acidic combustion products accumulated in the oil to which the additive is added that can be neutralized by the additive. The measurement of alkaline reserve is reported as total base number (TBN) which is the number of milligrams of potassium hydroxide equivalent to the amount of acid required to neutralize the alkaline constituents present in one gram of sample. An additive having a total base number higher than can be obtained from calcium petroleum sulfonate alone is commonly said to be “overbased” or, alternatively, is said to be “superbasic”.
Overbased calcium sulfonates are generally produced by carbonating a mixture of hydrocarbons, sulfonic acid, calcium oxide, or calcium hydroxide and promoters, such as methanol and water. In carbonation, the calcium oxide or hydroxide reacts with the gaseous carbon dioxide to form calcium carbonate. The sulfonic acid is neutralized with an excess of CaO or Ca(OH)2 to form the sulfonate. Known processes for overbasing calcium sulfonates produce high alkaline reserves of TBN of 300 to 400 mg KOH/gm or higher, which enables the formulator to use lower amounts of additive while maintaining equivalent detergency to protect the engine adequately under conditions of high acid formation in the combustion process.
The calcium carbonate component of the overbased calcium sulfonate forms the core of a calcium sulfonate micellar structure. The calcium carbonate is either in the amorphous form or one or more of its crystalline forms, such as calcite.
The lubricating oil art, particularly as directed to automotive crankcase and other engine oils, mandates a clear or substantially haze free product for requisite consumer aesthetics and acceptance. This need previously precluded the use of detergents with haze producing crystalline calcium carbonate.
It was recognized in U.S. Pat. No. 4,995,993 that large micellar crystalline calcium carbonate structures caused haze, and overbased sulfonate products containing crystalline calcium carbonates were always undesirable and therefore crystallization was to be avoided at all costs.
In “Colloidal Anti-wear Additives 2. Tribological Behavior of Colloidal Additives in Mild Wear Regime,” J. L. Mansot et al., Colloids and Surfaces A: Physico Chemical and Engineering Aspects, 75 (1993), pp. 25–31, it is indicated that for certain forms of an overbased sulfonate containing an amorphous calcium carbonate core, when in a 2% by weight dispersion in dodecane, and subjected to metallic friction surfaces, the calcium carbonate forms a polycrystalline film adherent to the metallic friction surfaces, which resultantly provides anti-wear protection. Mansot et al. thereby taught providing an overbased calcium sulfonate with an amorphous micellar structure that would then, under a mild wear regime, undergo transformation to microcrystalline agglomerates through an amorphous intergranular phase.
WO 0004113 discloses a process for producing soluble overbased calcite-containing detergents that are suitable for use in engine oil formulations.
U.S. Pat. No. 4,617,135 discloses a process for the preparation of overbased oil soluble magnesium sulfonates comprising contacting an acidic gas at a temperature between about 50° F. up to the reflux temperature of the mixture, with a mixture consisting essentially of a sulfonic acid or salt thereof, a volatile aliphatic or aromatic or chlorinated hydrocarbon solvent, a non-volatile diluent oil, a light magnesium oxide, water, methanol and combination of promoters, wherein the first promoter is one selected from an oil soluble naphthenic acid and an oil soluble carboxylic acid or salt thereof; and a second promoter being one selected from:
wherein X is one of H, OH, NH2, CO2H, OCOCH3 and SH, and Y is one of H, CH3 and CH2CH3, wherein the second promoter is less oil soluble than the first promoter; and (b) a water soluble C1–C6 carboxylic acid. The volatile components are stripped from the reaction mixture after absorption of the acidic gas is completed, to give an overbased magnesium sulfonate. Relatively small amounts of about 1.0 to 1.5% of the combined promoters produce overbased magnesium sulfonates of exceptionally high alkalinity value up to 500 or more, with minimum sediment.
U.S. Pat. No. 4,647,387 discloses an engine or lubricating oil containing 0.03 to 0.3% by weight of a succinic anhydride promoter reaction product for an overbased magnesium sulfonate, based on the presence of 0.5% by weight of Mg metal in the oil, and wherein the weight of the reaction product is commensurately proportional to the weight of Mg metal in the oil, and which oil is free of post sulfonate formation water-tolerance additives, nevertheless passes the rigorous Cummins water tolerance test. Copromoters such as a naphthenic acid and/or a salicylic acid may be employed.
U.S. Pat. No. 4,748,259 discloses mixtures of a metal salt of formula
and a metal salt of formula
in which formulae, Me is a metal ion of valency n, n is 2, 3 or 4, and each of the rings A and B independently of the other is unsubstituted or substituted by halogen, lower alkyl, lower alkoxy or an α-methylbenzyl radical, are prepared by reacting 2 moles of salicylic acid with at least 2 moles of a styrene compound of formula
and at least 2 moles of a styrene compound of formula
in which formulae, the benzene rings A′ and B′ are unsubstituted or substituted by halogen, lower alkyl or lower alkoxy, in the presence of an aromatic sulfonic acid, and, in a further step, reacting 2n moles of the resultant mixture of the salicylic acid compound of formula
and the salicylic acid compound of formula
in which formulae, A and B are as defined above, with 2 moles of the salt of an n-valent metal of an inorganic acid or of a lower aliphatic carboxylic acid, where n has the given meaning. The mixtures of metal salts are used as color formers in pressure- and heat-sensitive recording materials.
U.S. Pat. No. 4,810,398 discloses a basic alkaline earth metal salt of a blend of organic carboxylic acids that is prepared by (a) preparing a mixture of one equivalent of the blend of organic carboxylic acids and more than one equivalent of an alkaline earth metal hydroxide and/or oxide in a hydrocarbon solvent; (b) introducing carbon dioxide into the mixture obtained in an amount of at least 0.5 equivalent carbon dioxide per equivalent of excess alkaline earth metal; and (c) removing residual solids, if any, and an aqueous layer, if any, whereby the blend of organic carboxylic acids comprises a C8-30 alkyl salicylic acid and one or more alkanecarboxylic acids in which the alkyl moiety is branched and has from 4 to 40 carbon atoms. Such a salt has dispersant properties and is said to be suitable for use in lubricating oil and fuel compositions.
U.S. Pat. No. 4,832,857 discloses a process for incorporating molybdenum into overbased alkaline earth metal and alkali metal sulfonates, phenates and salicylates. The incorporation is a post addition of molybdenum into a previously prepared overbased composition. The resulting composition containing molybdenum is said to have a reproducible TBN and to be gel-free, haze-free, precipitate-free, and commercially acceptable for use in lubricating oil compositions.
U.S. Pat. No. 4,869,837 discloses a process for the preparation of a basic alkaline earth metal salt of a blend of organic carboxylic acids, which comprises (a) preparing a mixture of one equivalent of the blend of organic carboxylic acids and more than one equivalent of an alkaline earth metal hydroxide and/or oxide in a hydrocarbon solvent; (b) introducing carbon dioxide into the mixture obtained in an amount of at least 0.5 equivalent carbon dioxide per equivalent of excess alkaline earth metal; and (c) removing residual solids, if any, and an aqueous layer, if any, whereby the blend of organic carboxylic acids comprises an oil-soluble alkyl salicylic acid and one or more hydrocarbon substituted succinic acids or anhydrides, in which the hydrocarbon radical has a number average molecular weight from 120 to 5000.
U.S. Pat. No. 5,075,416 discloses a process for the preparation of an aromatic hydrocarbon resin modified with aromatic carboxylic acids comprising suspending methane sulfonic acid and at least one aromatic carboxylic acid in an aliphatic solvent and slowly proportioning at least one unsaturated aromatic hydrocarbon into the suspension under polymerization conditions and their salts.
U.S. Pat. No. 5,225,588 discloses alkylating hydroxybenzoates, such as methylsalicylate, by reacting a hydroxybenzoate with a polyalphaolefin in the presence of a catalytic amount of SnCl4.
U.S. Pat. No. 5,415,792 discloses overbased alkyl alkyl salicylate that are said to be useful additives for lubricating oil compositions that impart detergency and dispersancy to the lubricating oil composition and provide for alkalinity reserve.
U.S. Pat. No. 5,647,896 discloses a color-developing agent comprising a multivalent metal salt of a salicylic acid derivative and a sulfonated phenol and/or a metal salt thereof and having excellent initial and ultimate color-developing capacities and improved waterproofness; and a color-developing sheet making use of the color-developing agent.
U.S. Pat. No. 5,734,078 discloses a process for the production of an alkyl salicylic acid in which the alkyl substituent has at least 6 carbon atoms, comprising reacting salicylic acid with an olefin having at least 6 carbon atoms at elevated temperature in the presence of sulphuric acid as a catalyst. Lubricating oil additives comprising a metal salt of such alkylated salicylic acids and a process for making them are also disclosed.
U.S. Pat. No. 5,744,430 discloses a composition having therein a base oil with a specified kinematic viscosity and with a specified total amount of aromatics, comprising, in specified amounts based on the total weight of the composition: (b) an alkaline earth metal salicylate detergent; (c) a zinc dialkyldithiophosphate; (d) a succinimide ashless dispersant containing a polybutenyl group having a specified number-average molecular weight; (e) a phenol ashless antioxidant; (f) a molybdenum dithiocarbamate friction modifier; and (g) a viscosity index improver in such an amount that the kinematic viscosity of said composition ranges from 5.6 to 12.5 mm2/s at 100° C.
U.S. Pat. No. 6,197,075 discloses an overbased magnesium composition deposit control additive for residual fuel oils and turbine fuels that is an overbased magnesium sulfonate, carboxylate or phenate or mixtures thereof containing at least 14% and upwards to about 18% by weight of magnesium and containing a succinic anhydride and lower carboxylic acid co-promoter reaction product. The additive when added to fuel oils, such as residual fuel oils containing high asphaltenes, reduces, if not eliminates, magnesium/asphaltene deposits or sediment and the consequential plugging of filters. The additive also reduces, if not eliminates, vanadium caused corrosion in the turbine. Also disclosed is a process for preparing the overbased composition or deposit control additive, wherein the overbasing reaction incorporates the combination of a lower carboxylic acid, preferably acetic acid and a succinic anhydride, preferably dodecenyl succinic anhydride, as the co-promoter.
U.S. Pat. No. 6,303,550 discloses a lubricating oil composition comprising a di-block copolymer of poly(monovinyl aromatic hydrocarbon) and hydrogenated poly(conjugated diene) as a dispersant additive. The di-block copolymer preferably comprises poly(monovinyl aromatic hydrocarbon) in the molecular weight range 8,000–30,000. The diblock copolymers are said to be useful as dispersant additives in lubricant oils, reduce heavy metal corrosion, reduce degradation of elastomeric seals and are less sensitive to the presence of over-based detergents.
There remains a need in the art for a lubricating oil detergent with inherent improved high temperature detergency which also necessarily has commercially acceptable levels of minimal haze, or are essentially haze free, and acceptable minimal levels of turbidity. In particular, there remains a need for an automotive oil having improved detergency and antioxidant properties for use as a crankcase engine oil.
The compositions of this invention also are suitable for use in either low or medium speed engines especially marine diesel engines. Typically such engines are 4 stroke trunk piston engines having an engine speed of 50–1000 RPM. The engine can also be a 2 stroke cross head engine having a speed 40–1000 RPM.